The invention is based on a priority application EP 01 440 260.6, which is hereby incorporated by reference.
The invention relates to a method of operating a relay array using row and column addressing to improve discrimination between selected and non-selected relays.
In advanced technology, miniaturized relays are integrally formed in a substrate such as a printed circuit board. Such technology is described in the patent application EP 02 290 608.5. In a preferred embodiment of this arrangement, the relays are arranged in an array and a row and column addressing system is used to set or reset relays.
A known method of addressing relays in an array is to provide two windings on each relay, wherein one winding is associated with a row drive signal and one winding is associated with a column drive signal, and half of the required activation current is provided by each winding. A known limitation of such addressing arrangements is limited discrimination between selected relays and non-selected relays. The present invention relates to an enhanced addressing system for such arrays of relays.
The discrimination of row and column addressing in a relay array as described above can be improved by the use of xe2x80x9ccanceling currentsxe2x80x9d in the non-addressed relays.
False operation of relays can occur in a row and column addressing system with insufficient discrimination of activation current between addressed and non-addressed relays.
Discrimination can be increased by providing a current below the minimum trip current in the row coil of the selected relay, and providing twice this current in the column coil of the selected relay. In all the other rows, an opposite current equal to the first row current, but in the opposite direction is used to counteract the column current and reduce the net magnetic force to below the trip threshold for all relays in those other rows, except for the selected row, where the currents reinforce.
This gives a 3:1 discrimination between selected and non-selected relays. To prevent false operation, the below the trip threshold currents are applied before the double current is applied to the selected column.
While the invention is suitable for use in miniaturized relays, it can also be used with larger relays.